U.S. Pat. No. 4,375,877 to Shorey, whose contents are incorporated herein in their entirety by this reference, describes one of many possible emergency evacuation systems for vessels such as aircraft. Certain then-existing systems disclosed in the Shorey patent include sources of compressed air for inflating evacuation slides and “relatively complex actuation arrangements for activating the gas supply at a proper time within the system deployment sequence.” See Shorey, col. 2, ll. 21-23. Systems of the Shorey patent likewise utilize cylinders of compressed gas for inflation, with valves supplying the compressed gas being “actuated by trigger lanyards that extend upwardly from the valves.” See id., col. 5, ll. 67-68. The trigger lanyards connect to spring-loaded pins, and pulling of the pins actuate the valves. See id., col. 8, ll. 62-68. To reduce risk of premature inflation of the slides, shear pins are used. See id., col. 6, ll. 7-12.
Absent from description in the Shorey patent is any means for securing inflation pins in locked positions. Consequently, gas cylinders remain subject to premature deployment during packing, for example. Cylinders also may be inadvertently de-armed.